1. Field of the Invention
The present invention relates to authentication systems, authentication methods, authentication apparatuses, and authentication methods therefor, and more particularly, to an authentication apparatus which efficiently uses advantages of different types of encryption methods to perform encryption.
2. Description of the Prior Art
As authentication and signature methods in authentication systems, there have been conventionally used a common-key encryption method and a public-key encryption method.
In the common-key encryption method, one encryption key called a common key is used and information encrypted by the common key is decrypted by the same common key. Since the common-key encryption method performs encryption and decryption within a short period, it is used in cases where information which requires high-speed processing is processed, such as electronic money or commuter-pass information stored in an IC card.
In the public-key encryption method, two encryption keys called a public key and a private key are used, and information encrypted by one encryption key is decrypted by the other encryption key. The public-key encryption method has a higher safety in terms of information leakage but has a lower processing speed than the common-key encryption method, and is used in cases where anonymity is required, such as a case in which a financial transaction is achieved on a network, such as the Internet.
When the public-key encryption method is used, an IC card stores a certificate for certifying the user who uses the IC card and a public key, and is used as an encryption module.
Depending on fields to which authentication systems are applied, the common-key encryption method or the public-key encryption method is used.
It has been demanded these days, however, that an encryption method be created which has both safety provided by the public-key encryption method and quickness provided by the common-key encryption method, in order to allow one IC card to enable efficient authentication and a financial transaction.
Authentication systems have the ability to check the legitimacy of a certificate stored in an IC card, but do not have the ability to check whether the IC card is actually used legitimately.
In authentication systems, if an IC card is lost, since procedures for authentication and a financial transaction by the use of the IC card is stopped according to a certificate invalidation list periodically issued from a certification authority provided on a network, the use of the IC card performed real time at any points on the network cannot be stopped immediately.